Prevention of hydrogen fires in chlorine cells

ABSTRACT

HYDROGEN FIRES IN DIAPHRAGM-TYPE CHLORINE CELLS ARE PREVENTED BY PROVIDING A CHEMICALLY-INERT, NON-CONDUCTING, NON-WETTING ANNULAR INSERT IN THE HOSE WHICH CONNECTS THE HYDROGEN HEADER WITH THE CELL CAN.

United States. Patent Oihce 3565973 Patented Feb. 23, 1971 chemically inert, non-conducting, non-wetting material.

3,565,773 With the prevention of these salt bridges, and conse- P FIRES quently the prevention of hydrogen fires, not only is the Marvin L. Moore, Mentor, Ohio, and Phillip H. Sears, hazam to P63011961 a eqllipment removed but e a Houston, Tex assignors to Diamond Shamrock considerable savings 1s realized in that the connecting pany, Cleveland, Ohio, a corporation of Delaware hoses need not be replaced as Often- No Drawing. Filed Sept. 13, 1968, Scr. No. 759,779 In order to illustrate the practice of the present in- Int. Cl. B01k 1/00, 3/00 vention, several test cells which previously have been Cl- 2041 3 2 Clalms particularly susceptible to hydrogen fires are provided with modified connecting hoses according to the practice of the present invention. These test cells previously had ABSTRACT OF THE DISCLDSURE an average hose life of from 56 days with a range of Hydrogen fi i di h z hl i ll are from 0.5 to 10 days. Each of the connecting hoses, which prevented by providing a chemically-inert, non-conducthave an internal diameter of 3.25 inches, is fitted with a ing, non-wetting, annular in ert i th h whi h o two inch wide annular insert which consists of sections meets h h d h d i h 11 of polytetrafluoroethylene tubing having an external diameter of 3.25 inches and a wall thickness of 0.08 inch. These inserts are located in the hose approximately two BACK 0 THE INVENTION to three inches below the nozzle from the hydrogen header. In all instances the inserts completely eliminate hydrogen fires on the test cells and the hoses do not fail after a service life of from 7093 days.

It has been estimated that in a cell room currently requiring 1,400 replacement hoses per year, only 1,000 hoses per year will be required if the cells normally subject to hydrogen fires are provided with the annular inserts of the present invention. The only reason for replacing the hoses will then be that chemical deterioration of the rubber has taken place.

A number of materials are useful according to the present invention for fabricating the annular inserts, the primary consideration being that these materials are chemicell room, there is the not insubstantial problem of fallure Camhinert, nomconductive and nomwetting Examples of i the rubber hoses the replaeement of Whleh adds such compounds are polytetrafluoroethylene and polyvinylslderaele expense to the opeeatlon of the eeu roomfluoride. It will be obvious to those skilled in the art that,

Whlle a number of selutlons have been propesee to while chemical inertness is extremely desirable, a certain end thls m Such formmg theee hoses enmely amount of instability can be tolerated if the annular infrom a non-wetting material, these solutions have proven serts are periodically discarded to too expensive for commercial applieafion' Although the invention has been described with refer- A common problem in cell rooms containing a large number of diaphragm-type cells for the production of chlorine and caustic is the occurrence of hydrogen fires. In these cell rooms, hydrogen outlets extend from the individual cell cans and are connected to the hydrogen header, usually by means of flexible natural rubber hoses. Hydrogen fires are believed to be caused by electrical shorting through the caustic soda-salt bridge which deposits on the inner wall of the rubber hose. These hydrogen fires naturally occur most frequently on cells having 30 the highest voltage to ground. In addition to the obvious hazard of these fires to personnel and equipment in the STATEMENT OF THE INVENTION 40 ence to certain preferred embodiments thereof, it is not to be so limited since changes and alterations may be Therefore it is the primary object of this invention to made therein which are within the full and intended scope provide an economical and eifective means for preventing of the appended claims. hydrogen fires in diaphragm-type cells. What is claimed is:

This and further objects and advantages of the present 1. In a method of operating an electrolytic diaphragm invention will become apparent to those skilled in the art cell which includes a cell can, a hydrogen header and a from the description and claims which follow. hose of wettable material connecting said can and header It has now been found that hydrogen fires resulting the improvement comprising, providing said hose with an from the formation of caustic soda-salt bridges in the annular insert engaging the inner wall thereof, said insert hoses connecting diaphragm cells with hydrogen headers being composed of a chemically-inert, non-conducting, may be substantially completely prevented by the pronon-wetting material, whereby hydrogen fires are subvision in the hoses of annular inserts of a chemicallystantially prevented. inert, non-conducting, non-wetting material. 2. A method as in claim 1 where the annular inert comprises polytetrafluoroethylene. DESCRIPTION OF THE PREFERRED EMBODIMENTS References Cited As is set forth hereinabove, it is believed that the pri- UNITED STATES PATENTS mary cause for the hydrogen fires which occur in dia- 2,890,157 6/1959 Raetzsch 2O498 phragm-cell operation is the formation of electrically con- 3,045,665 7/1962 Moyat ductive caustic soda-salt bridges between the hydrogen 3,113,080 12/1963 Andrus 204 73 header and the cell can. These salt bridges result from 3 9/ 1968 Messner 204-1 the deposition of the various salts present in the catholyte 3,400,069 9/ 1968 Dreckmann 204-278 on the inside of the rubber hoses. The formation of this caustic soda-salt bridge can then lead to electrical short- JOHN MACK Primary Exammer ing between the cell and the grounded header. Surpris- A C PRESCOTT, A i t t E i ingly, it has been found that the formation of these salt bridges may be prevented by the provision in the connect- US. Cl. X.R. ing hose of as little as a two inch annular insert of a 204256, 258 

